This entire module is devoted to modeling scenarios and solving problems dealing with fluid flowing through a fixed control volume. That fluid can be a liquid (such as water) or a gas (such as air). The control volume can be something man-made (such as a building) or something natural (such as a lake). While this program focuses on the theme of contaminants flowing into a lake, the same equations appearing in this module can also be used to model many other scenarios. We include a few examples below.